1. Field of the Invention
The present invention relates to a portable information equipment such as a notebook computer or the like and particularly relates to a metallic case for use in the portable information equipment and a manufacturing method of the case.
2. Background Art
In recent years, the portable information equipment such as a notebook computer or the like has been made thinner and lighter to enhance the portability, the case forming an outer shell has also been made in a thinner profile. Meanwhile, the case has been made of a metallic material to improve mechanical strength, in order to protect electromagnetic interference (EMI) and to dissipate heat generated inside the equipment efficiently.
A conventional portable information equipment is described below with reference to the drawings. FIG. 7A shows an outward perspective view of a conventional portable information equipment in a state that a display unit is opened, and FIG. 7B shows the same in a state that the display unit is closed. FIG. 8A shows a cross-sectional view of the display unit taken along the line 8A-8A in FIG. 7B, and FIG. 8B shows the same taken along the line 8B-8B in FIG. 7B.
Display unit 32 is joined with body 31 of the equipment via hinge 33 which makes the both can be opened and closed. In display unit 32, a liquid crystal display drive (LCD drive; not shown) and LCD panel 36, which are components to form an LCD display device, are disposed between rear case 34 and front frame 35.
The portable information equipment has generally, as is called a note type or a book type, a thin box shape with a rectangular flat portion to put into a bag or the like suitably. Rear case 34 is made of a metallic material such as aluminum or the like to improve mechanical strength so as to protect EMI and to dissipate heat generated inside the equipment efficiently. To reduce weight of the equipment, especially in recent years, magnesium alloy having lower specific gravity and greater strength than aluminum is used to realize an utmost thin case thickness. The advance in thin-and-light design has increased further chances for the equipment to be carried around in a bag or the like. However, when a person carrying a bag gets on a crowded train, the bag receives a high pressure from outside. The pressure will be applied on display unit 32 of the equipment if packed in the bag. Measures have been studied variously to prevent thin walled rear case 34 from being deformed by the pressure to break LCD panel 36 housed therein. That is, Unexamined Japanese Patent Publication No. 2003-204174 discloses a technology that is to form a non-flat rear case 34 like a car-hood as shown in FIGS. 7B and 8A while a thin thickness is maintained. Additionally, Unexamined Japanese Patent Publication No. H09-62400 discloses a technology to provide the entire case surface with ribs. These structures improve the mechanical strength of rear case 34.
In some cases, however, even such structures cannot perfectly prevent LCD panel 36 from being broken. Therefore, rear case 34 is required to improve further its mechanical strength.